A good fasting blood glucose level is below 100 mg/dL. After eating, a healthy reading stays below 140 mg/dL when measured two hours after a meal. These are the benchmarks for people without diabetes, but the numbers shift depending on whether you’re managing diabetes, pregnant, or older with other health conditions.
Healthy Fasting Glucose
Fasting glucose is measured after at least eight hours without eating, which is why it’s typically drawn first thing in the morning. Below 100 mg/dL is normal. Once you hit 100 to 125 mg/dL, you’re in the prediabetes range. A fasting level of 126 mg/dL or higher on two separate tests meets the diagnostic threshold for diabetes.
These cutoffs aren’t arbitrary. The range between 100 and 125 signals that your body is starting to struggle with processing sugar efficiently, even if you feel perfectly fine. Roughly 98 million American adults have prediabetes, and most don’t know it, which is why a routine fasting glucose test can catch the problem years before symptoms appear.
After-Meal Glucose Levels
Blood sugar naturally rises after you eat and then comes back down as your body moves glucose into cells for energy. In a person without diabetes, levels peak somewhere around one hour after eating and return close to baseline by two hours. At the two-hour mark, a normal reading is below 140 mg/dL. If it’s still above 140 at two hours, that suggests your body isn’t clearing glucose efficiently.
The type of food matters enormously. A meal heavy in refined carbohydrates (white bread, sugary drinks, white rice) will spike your blood sugar faster and higher than a meal built around protein, fat, and fiber. Two people with identical fasting numbers can have very different post-meal responses depending on what and how they eat.
What the Numbers Mean for Prediabetes and Diabetes
Doctors use three main tests to diagnose prediabetes and diabetes, and each has its own set of cutoffs:
- Fasting glucose: Below 100 is normal. 100 to 125 is prediabetes. 126 or higher is diabetes.
- A1C (a measure of your average blood sugar over 2 to 3 months): Below 5.7% is normal. 5.7% to 6.4% is prediabetes. 6.5% or higher is diabetes.
- Oral glucose tolerance test (blood drawn 2 hours after drinking a sugary solution): Below 140 is normal. 140 to 199 is prediabetes. 200 or higher is diabetes.
A single high reading doesn’t automatically mean diabetes. Doctors typically confirm the diagnosis with a second test on a different day, unless your blood sugar is above 200 and you’re already experiencing symptoms like excessive thirst, frequent urination, or unexplained weight loss.
Targets If You Have Diabetes
If you’ve already been diagnosed with diabetes, “good” glucose levels are less strict than normal healthy ranges, because pushing too aggressively toward non-diabetic numbers can increase the risk of dangerous lows. The American Diabetes Association recommends these targets for most adults with diabetes:
- Before meals: 80 to 130 mg/dL
- One to two hours after starting a meal: Below 180 mg/dL
- A1C: Below 7%, which translates to an estimated average glucose of about 154 mg/dL
These are general guidelines. Your doctor may set a tighter or more relaxed target depending on how long you’ve had diabetes, what medications you take, and your risk for low blood sugar episodes.
When Blood Sugar Drops Too Low
Low blood sugar, or hypoglycemia, is anything below 70 mg/dL. It causes symptoms like shakiness, sweating, confusion, irritability, and a rapid heartbeat. Below 54 mg/dL is considered severe and can lead to seizures or loss of consciousness if untreated.
Hypoglycemia is primarily a concern for people taking insulin or certain other diabetes medications. It’s uncommon in people without diabetes, though it can happen after prolonged fasting, intense exercise, or excessive alcohol consumption. If you experience symptoms, consuming 15 to 20 grams of fast-acting carbohydrates (a few glucose tablets, half a cup of juice) and rechecking after 15 minutes is the standard approach.
Glucose Targets During Pregnancy
Pregnancy tightens the acceptable glucose range because high blood sugar can affect fetal development. The American College of Obstetricians and Gynecologists recommends these targets for pregnant women with diabetes:
- Fasting: Below 95 mg/dL
- One hour after eating: Below 140 mg/dL
- Two hours after eating: Below 120 mg/dL
These numbers are lower than the standard diabetes targets because even modestly elevated glucose crosses the placenta and can cause the baby to grow too large, increasing the risk of delivery complications. Women with gestational diabetes typically monitor their blood sugar four or more times daily to stay within these ranges.
Adjusted Targets for Older Adults
For older adults managing diabetes, targets often become more relaxed, not less important. The reasoning is straightforward: the older you are and the more health conditions you have, the greater the danger from low blood sugar. A hypoglycemic episode that might cause mild shakiness in a 40-year-old can trigger a fall, a fracture, or a cardiac event in someone who is 80 and frail.
Healthy, independent older adults with a life expectancy over 10 years are generally held to the same A1C target of 7% or below. But for those who are frail, have dementia, or depend on others for daily care, guidelines loosen the A1C target to below 8.5%. The priority shifts from preventing long-term complications to avoiding dangerous lows and keeping the person comfortable day to day.
Continuous Glucose Monitors and Time in Range
If you wear a continuous glucose monitor (CGM), you’ll see a metric called “time in range,” which tracks what percentage of the day your blood sugar stays between 70 and 180 mg/dL. For most people with type 1 or type 2 diabetes, the goal is to spend more than 70% of the day in that window. That works out to roughly 17 hours.
Equally important are the time-below-range targets: less than 4% of the day below 70 mg/dL, and less than 1% below 54. On the high end, the goal is to keep readings above 250 mg/dL to less than 5% of the day. Time in range gives a much richer picture than a single fasting number because it captures the full pattern of spikes and dips across meals, sleep, and activity. Each 5% improvement in time in range corresponds to a measurable reduction in A1C, so even incremental gains matter.
What Affects Your Numbers Day to Day
Blood sugar is not a fixed value. It fluctuates throughout the day in response to food, physical activity, stress, sleep quality, illness, and hormonal cycles. A fasting reading of 95 one morning and 105 the next doesn’t necessarily signal a problem. Single readings are snapshots, and context matters.
Exercise lowers blood sugar both during and after activity by helping muscles absorb glucose without needing as much insulin. Stress and poor sleep do the opposite, raising blood sugar through the release of hormones like cortisol and adrenaline. Even the order in which you eat foods at a meal can make a difference: eating protein and vegetables before carbohydrates tends to blunt the post-meal spike. If you’re tracking your numbers, logging meals and activities alongside your readings will reveal your personal patterns far better than memorizing a single target range.